Rockwell-automation 1761 MicroLogix 1000 Programmable Controllers Manual de usuario descargar pdf (Pagina 173)

100

101

Using Data Handling Instructions

9–25

FIFO Load (FFL) and FIFO Unload (FFU)

FFL and FFU instructions are used in pairs. The FFL instruction loads words into a

user-created file called a FIFO stack. The FFU instruction unloads words from the

FIFO stack in the same order as they were entered.

Operation

Instruction parameters have been programmed in the FFL – FFU instruction pair

shown below

(EM)

(EN)

(DN)

(EM)

FFL

FIFO LOAD

Source N7:10

FIFO #N7:12

Control R6:0

Length 34

Position 9

(EU)

FFU

FIFO UNLOAD

FIFO #N7:12

Dest N7:11

Control R6:0

Length 34

Position 9

FFU

instruction unloads data

from stack #N7:12 at position 0,

N7:12.

N7:12

N7:13

N7:14

34 words are allocated

for FIFO stack starting at

N7:12, ending at N7:45.

FFL–FFU Instruction Pair

Loading and Unloading of Stack #N7:12

N7:10

N7:11

PositionDestination

Source

FFL instruction loads data into

stack #N7:12 at the next available

position, 9 in this case.

N7:45

(DN)

FFL Instruction

When rung conditions change from false-to-true, the controller sets the FFL enable

bit (EN). This loads the contents of the Source, N7:10, into the stack structure

indicated by the Position number, 9. The position value then increments.

The FFL instruction loads an element at each false-to-true transition of the rung,

until the stack is filled (34 elements). The controller then sets the done bit (DN),

inhibiting further loading.

Programming

Execution Times

(µsec) when:

True False

61.13 33.67

1 2 ... 168 169 170 171 172 173 174 175 176 177 178 ... 421 422

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